For a purely competitive firm, the price equals:

In a purely competitive market, the price a firm receives for its products is equal to the average revenue it generates from selling those products. This occurs because, in perfect competition, firms are price takers and the price is determined by the market. Consequently, for a competitive firm, the price charged for each unit of a good is identical to the average revenue that the firm earns per unit.

Since the firm can sell as much as it wants at the market price without affecting that price, the marginal revenue (the additional revenue from selling one more unit) also equals the price. While marginal cost is critical in determining the profit-maximizing output level, it does not directly define the relationship between price and revenue in this context.

Understanding the relationship between price, marginal revenue, and average revenue is crucial as it illustrates how firms in purely competitive markets operate efficiently and respond to market conditions without being able to influence prices.